[0001] This invention relates to textile pigment printing, and in particular to the production
of a printed textile fabric wherein the printed areas are of a predetermined desired
color and are characterized by being substantially opaque and thus unaffected by the
color of the underlying yarns. This invention is related to and is an improvement
over the inventions described in U.S. Patent 4,438,169 issued March 20,1984 and U.S.
Patent 4,457,980 issued July 3, 1984.
[0002] These patents disclose a unique new type of textile printing process and product
in which the printed areas on the textile fabric are substantially opaque and are
thus unaffected by the color of the underlying yarns. The aqueous opaque printing
process and product of these earlier applications overcome a number of significant
limitations and disadvantages of conventional pigment printing techniques and enable
the production of a wide variety of patterns and colors not obtainable by the pigment
printing techniques heretofore known. The printing paste which is used in the opaque
printing process, unlike the aqueous printing pastes used in conventional screen printing
operations, has opacity and can be applied over either dark or light background fabrics
without being affected by the color of the underlying yarns. The resulting printed
pattern areas on the fabric comprise an opaque coating which covers the exposed surfaces
of the yarns which form the fabric. This coating comprises an opacifying pigment providing
opacity in the coating and a cured water insoluble polymer binder which is affixed
to the yarns and bonds the opacifying pigment to the yarns. The opaque coating which
forms the printed pattern areas is characterized by individually coating each of the
yarns in the printed area such that the interengaged yarn structure of the fabric
is not obliterated, but remains visible. More specifically, the opaque coating at
the surface of the yarn is such that the individual surface fibers of the yarn also
are not obliterated and remain visible.
[0003] The opaque coating which forms the printed pattern areas may be of any desired color.
For relatively light colors, such as white, the opacifying pigment itself may be utilized
for providing the desired colors. Other colors may be produced by including colored
pigments or dyestuffs in the printing paste in addition to the opacifying pigment.
[0004] The printing paste is applied to the fabric as a stable aqueous dispersion of the
opacifying pigment and polymer binder. After printing on the fabric, the printing
paste is dried and cured by heating, with a crosslinking reaction taking place, such
that the polymer binder is converted from the aqueous solution or dispersion as it
is applied to a tough flexible water insoluble pigmented opaque film. More particularly,
the printing paste formulations described in the aformentioned applications rely on
acrylic latex and/or aminoplast resins for crosslinking during curing.
[0005] The present invention provides an alternative procedure for producing cured aqueous
opaque textile prints which offers a number of advantages over the above- described
system of the commonly-owned copending applications referred to earlier. In producing
opaque printed areas on textile fabrics in accordance with the present invention,
a printing paste is utilized which contains the opacifying pigment and a binder which
is comprised of monomeric, oligomeric and/or polymeric units capable of being polymerized
and cured by free radical initiation. After application of the printing paste to the
fabric, the fabric is subjected to free radical initiation to polymerize and cure
the binder and thereby bond the opacifying pigment to the yarns.
[0006] In accordance with one aspect of the invention, the polymerizable binder is a radiation
curable binder, and the fabric is subjected to free radical initiation by irradiating
the fabric with high energy radiation.
[0007] In another embodiment of the invention, the polymerizable binder additionally contains
a free radical initiator, which may be activated by suitable means such as heating
or exposure to radition; and by activating the initiation, the fabric is subjected
to free radical initiation to thereby polymerize and cure the binder.
[0008] An advantage of the free radical curing procedure of the present invention is that
the printing paste does not require the presence of a catalyst, which sometimes causes
yellowing or discoloration of the fabric under curing conditions. Atmospheric pollutants,
associated with solvent systems such as in conventional opaque stencil printing are
also eliminated. Additionally, this procedure in many instances makes it possible
to carry out curing at a lower temperature, which has many advantages, such as energy
savings, reducing fabric shrinkage, and permitting the curing to be carried out at
a faster rate.
[0009] Some of the features and advantages of the invention having been stated, others will
become apparent from the detailed description and examples which follow, and from
the accompanying drawing, which is a schematic illustration of an arrangement of apparatus
suitable of carrying out the process of this invention.
[0010] The aqueous opaque colored printing paste of the present invention has a relatively
high solids content, e.g. preferably at least 25 percent total solids, and consists
mainly of an opacifying pigment and a free radical polymerizable binder mixed therewith
to form a stable aqueous dispersion.
[0011] To serve as an opacifying pigment for purposes of this invention, the material must
be highly opaque, have color properties which permit it to be used alone or mixed
with other colorants, such as dyes and colored pigments, and it must be readily dispersable
at relatively high concentrations in the aqueous binder system. There are many commercially
available materials having these characteristics. Where it is desired to provide a
relatively light colored printed area, particularly against a relatively darker background
color, the preferred opacifying pigment for use in the printing paste formulation
of this invention is a white pigment. One particular white pigment which has been
found to be especially suitable because of its bright white appearance, cost and availability
is titanium dioxide. Other suitable white pigments include silicates, aluminum compounds,
calcium carbonate, and the like. In order to achieve high chroma (color saturation)
with certain hues, one or more opacifying pigments of lesser whiteness or of intermediate
shades may be employed, either alone or in combination with white pigments.
[0012] In addition to the white opacifying pigments noted above, examples of other compounds
suitable for use as opacifying pigments in the present invention include the following:
zinc oxide, zinc sulfide, lithopone (ZnS/BaS0
4), basic carbonate white lead, basic sulfate white lead, lead oxide (lead dioxide),
calcium sulfate, barium sulfate, silica, clay (Al
2O
3·2SiO
2·2H
2O), lead sulfate, magnesium silicate, mica, wollastonite (CaSi0
3), aluminum hydrate, magnesium oxide, magnesium carbonate, aluminum oxide, ferric
oxide, sodium carbonate, strontium sulfide, calcium sulfide, barium carbonate, antimonius
oxide, zirconium white, barium tungstate, bismuth oxychloride, tin white, lead silicate,
chalk, bentonite, barium sulfate, gloss white, gypsum, zinc phosphate, lead phosphate,
and calcium silicate. For the printing of relatively dark colors, carbon black may
be used as an opacifying pigment instead of a lighter colored pigment.
[0013] The use of an opacifying pigment, particularly a white opacifying pigment, and the
printing thereof against a darker background color, are features which clearly distinguish
the opaque pigment printing of this invention over conventional non-opaque pigment
printing techniques. In conventional pigment printing, white pigments are used only
on a white or light shade background fabric for achieving a "white- on-light" effect.
Conventional pastel or white pigment printing pastes are not generally applied to
darker background colors, since such printing pastes would not provide adequate uniform
opacity against the darker background color.
[0014] The amount of the opacifying pigment used in the printing paste formulation of this
invention is considerably greater than the amount of pigment used in conventional
aqueous-based non-opaque printing pastes, and is typically considerably greater than
the total solids content of the polymer binder. In a preferred formulation, the printing
paste comprises at least 20 weight percent opacifying pigment (solids basis) and at
least 5 weight percent polymer binder (solids basis).
[0015] The binder for the opacifying pigment must be capable of application in an aqueous
system, form a stable dispersion with the insoluble opacifying pigments and other
additives in the binder system, have good film-forming properties when applied to
the fabric, and must be capable of being dried and cured to a water insoluble state
imparting good washfastness and abrasion resistance properties to the printed pattern.
The polymer binder may be suitably applied as an aqueous solution or dispersion. The
print paste may be thereafter dried to a desired degree by suitable means, such as
by heating, and cured via free radical curing as described more fully herein.
[0016] The mechanism involved in free radical curing of the printing paste in accordance
with the present invention is significantly different from that in conventional thermal
curing. In the latter, strong catalysts, such as p-toluenesulfonic acid may be employed
with cross-linking agents which cure when the printing paste is subjected to elevated
temperatures. Free radical curing relies upon the presence of free radicals for the
initiation of a free radical addition polymerization reaction. Thus, in order to achieve
the curing, selected monomers, oligomers, polymers, or mixtures of these are included
in the print paste which contain functional groups which are susceptible to free radical
addition polymerization.
[0017] Generation of the free radicals needed to initiate the polymerization reaction may
be accomplished in a number of different ways. Certain compounds, such as styrene
for example, will polymerize by free radical polymerization with application of heat
alone. Other compounds require free radical initiators to provide the free radicals
necessary for the free radical polymerization reaction to take place. The free radical
initiators may be in the form of chemical compounds which will generate free radicals
upon being subjected to certain influences, such as heating or radiation. Examples
of chemical compounds which may be used as initiators to generate free radicals with
heating include, but are not limited to, benzoyl peroxide, acetyl peroxide, azodiisobutyronitrile,
t-butylhydroperoxide, cumene hydroperoxide, t-butylperoctoate, di-t-butyl peroxide,
succinyl peroxide, dicermyl peroxide, dichlorobenzoylperoxide, azodicyclohexylcarbonitrile,
and ethoxyethoxyethyl acrylate. Examples of monomers, oligomers and/or polymers that
are capable of curing through free radical addition polymerization include, vinyl
monomers, substituted ethylenes, conjugated dienes, non-conjugated dienes, polysiloxanes,
N-vinyl-2-pyrrolidone, 2-methyl butadiene, vinylnaphthalene, glycol dimethacrylate,
vinylacetate, acrylamide, methyl acrylate, methyl methacrylate, pentaerythritol acrylate,
vinyltriethoxy silane, vinyl functional polydimethylsiloxane, curable urethane monomers,
etc.
[0018] As an alternative to the use of chemical free radical initiators, it is possible
to initiate free radical polymerization by irradiation with actinic radiation. The
most well known methods of radiation curing are electron beam (EB) curing and ultraviolet
light (UV) curing. Typically, UV curing requires the inclusion of a photoinitiator
for free radical generation. EB curing, on the other hand, relies on the generation
of free radicals via the transfer of kinetic energy from the accelerated electron
to the polymer. There are a wide range of monomers, oligomers and polymers which are
suitable for high energy irradiation curing. These include, but are not limited to,
acrylate and methacrylate monomers and oligomers such as acrylated epoxies, urethanes,
polyesters and acrylics, multifunctional monomers, maleates, vinyl compounds such
as vinylethyl ethers, linear polyesters, and maleates or itaconates of mono or polyhydric
alcohol, and N-vinyl-2-pyrrolidone.
[0019] In addition to the opacifying pigment and free radical curable binder, the printing
paste may optionally include colorants, such as colored pigments or dyes, for providing
the desired color to the printing paste.
[0020] The dyes which may be suitably employed for coloring the binder may comprise at least
one member selected from the group consisting of acid dyes, cationic dyes, direct
dyes, disperse dyes, fiber reactive dyes, mordant dyes, and solvent dyes. Azoic dyes,
vat dyes, and sulfur dyes may also be used; however, the azoic compounds, vat dyes
and unreduced sulfur dyes would in effect behave as pigments since in the unreduced
form they are insoluble.
[0021] Silicone fluids and elastomers may be incorporated into the printing paste to aid
in obtaining a smooth application of the pigment to the fabric. The use of silicone
polymers has been found to provide dots or designs free of rough edges and crack marks.
[0022] Conventional thickeners may also be utilized to control the viscosity and rheology
of the paste, depending upon the size and design of the print pattern and the running
speed of the print screen.
[0023] The paste may also contain other conventional additives, such as emulsifiers, antifoam
agents, and pH control agents. It is important that the printing paste have good wetting
and film-forming properties so that when applied to the fabric, it will penetrate
and coat the individual yarns of the fabric rather than remaining on the surface of
the fabric. If these properties are not adequately presented by the polymer binder
itself, suitable wetting agents or emulsifiers may be included.
[0024] The printing paste may be applied either to uncolored (e.g. white) fabrics or to
precolored fabrics, the precolored fabrics being of a predetermined color throughout
and produced by any suitable method such as by piece dyeing, yarn dyeing or by pigment
padding, for example.
[0025] The particular rate of application of the printing paste to the fabric will vary
depending upon various factors, including fabric weight and construction, color of
the fabric, and printing color.
[0026] Drying and curing of the printing paste may be carried out under conditions of temperature
and time suitable for the particular manner of application and curing mechanism employed.
For rotary screen printing of a paste containing thermally activated chemical free
radical initiators, for example, drying and curing may be carried out at temperatures
of 250 to 425 degrees F. (121 to 218 degrees C.) for from several seconds up to several
minutes.
[0027] When the fabric is cured and dried, the areas printed with the printing paste are
characterized by having a thin flexible opaque coating covering the exposed surfaces
of the yarn and thus hiding from view the underlying color of the yarn. The coating
consists predominantly of the opacifying pigment bonded securely to the yarns by the
cured water insoluble polymer binder.
[0028] An arrangement of apparatus suitable for carrying out the process of the present
invention is schematically illustrated in the drawing. As shown, a fabric F is advanced
from a suitable supply source, such as roll 10 through a rotary printing range, generally
indicated at 12 consisting of a series of rotary printing cylinders., Rotary textile
printing ranges are well known in the art, and therefore a detailed description of
its construction and operation is not warranted.
[0029] After leaving the printing range 12, the fabric is advanced through a heating zone
14 for drying the printing paste. The heating zone 14 may suitably comprise a heated
tenter frame as is conventional in the art.
[0030] When curing a free radical curable binder containing thermally activatable free radical
initiators, the heat provided in the heating zone l4 alone is sufficient for generating
the free radicals necessary for polymerization and curing. As shown in the drawing,
however, for radiation curable compositions, a radiation source l6, such as ultraviolet
lamps or an electron curtain, may be located upstream from the heating zone for directing
radiation onto the fabric for thereby initiating free radical generation and curing.
Alternatively, the electron curtain 16 may be located downstream from the drying zone
14. After drying and curing of the printing paste has been been effected, the fabric
F may be taken up on suitable means such as a roll 18 as illustrated.
[0031] Because of the excellent opacity of the aqueous opaque colored printing paste formulations
of the present invention, which permits printing vivid contrasting colors on predyed
fabrics of any desired color, and the fact that the printing paste formulations of
this invention can be readily applied on conventional rotary screen printing equipment,
the present invention makes it possible to produce a variety of colors and patterns
not heretofore possible. Thus, one additional aspect of the present invention is the
production of a printed textile fabric formed of precolored yarns, and in particular
dyed yarns of a predetermined color, selected areas of the fabric having printed pattern
areas of predetermined color contrasting with the color of the yarns, the printed
pattern areas being substantially opaque and thus unaffected by the color of the yarns,
and the pattern areas being formed of a plurality of colors contrasting with one another
and with said predetermined color of the yarns, at least one of the colors being lighter
than said predetermined color dyed yarns, and said pattern areas comprising a filmlike
coating covering the exposed surfaces of the yarns, said coating comprising an opacifying
pigment providing opacity in said coating and a free radical cured binder securely
bonding said opacifying pigment to the yarns.
Examples 1 and 2
[0032] The following examples illustrate opaque print paste formulations which use addition
polymerization reactions initiated by chemically generated free radicals to promote
curing.

The print pastes are brought to a suitable viscosity with a conventional print paste
thickener, depending on the type printing machine employed -- rotary screen, flatbed,
etc. The fabric is then printed and cured as normal at approximately 360°F (182°C)
or thermosoled up to 425°F (218°C).
Examples 3 and 4
[0033] The following examples illustrate opaque print paste formulations containing irradiation
curable monomers.

The viscosity of the print paste is adjusted tc that necessary for the particular
printing machine used, rotary screen, flatbed, etc. using a conventional printing
thickener. After printing the fabric may either be dried in a conventional oven, then
irradiated or simply irradiated immediately after printing, depending on the drying
achievable during irradiation. Duration of irradiation depends on the type of irradiation
equipment employed; U.V., electron beam, electron curtain, etc., and the intensity
of the dose rate.
[0034] In the drawings and specification, there has been set forth a preferred embodiment
of the invention, and although specific terms are employed, they are used in a generic
and descriptive sense only and not for purposes of limitation.
1. A process of producing a textile fabric having printed areas thereon which are
substantially opaque and unaffected by the color of the underlying yarns, said process
comprising applying to selected portions of the fabric an opaque coating of a printing
paste covering the exposed surfaces of the yarns and hiding the underlying color thereof,
characterized in that said printing paste comprises an opacifying pigment and a polymerizable
binder comprised of free radical polymerizable monomeric, oligomeric and/or polymeric
units, and in that the applied printing paste on the fabric is subjected to free radical
initiation to polymerize and cure the binder and thereby bond the opaque coating to
the yarn.
2. The process according to claim 1, wherein said polymerizable binder comprises a
radiation curable binder, and said step of subjecting the fabric to free radical initiation
comprises irradiating the fabric with high energy radiation.
3. The process according to claim 1, wherein said polymerizable binder also comprises
a heat activatible free radical intitiator, and said step of subjecting the fabric
to free radical initiation comprises heating the fabric to activate said free radical
initiator.
4. The process according to any preceding claim, wherein the printing paste composition
comprises a stable aqueous dispersion of the opacifying pigment and polymerizable
binder.
5. The process according to any preceding claim, wherein the printing paste composition
has a solid content of at least 30 percent by weight.
6. The process according to any preceding claim, wherein said step of applying the
printing paste to the fabric comprises applying the printing paste to a precolored
fabric.
7. The process according to claim 6, wherein the precolored fabric is of a relatively
dark color and the printing paste is of a contrasting lighter color.
8. A printed textile fabric formed of interengaged yarns of a predetermined color,
selected areas of said fabric having printed pattern areas of predetermined color
contrasting with the color of said yarns, said printed pattern areas being substantially
opaque and thus unaffected by the color of said yarns, and said pattern areas comprising
an opaque coating covering the exposed surfaces of the interengaged yarns, said coating
comprising an opacifying pigment providing opacity in said coating and a free radical
polymerized binder bonding said opaque coating to the yarns.
9. A printed textile fabric according to claim 8, wherein said coating additionally
includes colored pigments for providing a predetermined desired color to the printed
pattern areas.
10. A printed textile fabric according to claim 8, wherein said coating additionally
includes dyestuffs for providing a predetermined desired color to the printed pattern
areas.
11. A printed textile fabric according to any one of claims 8 to 10, wherein the polymer
binder is a radiation cured polymer.
12. A printed textile fabric according to claim 11, wherein said coating additionally
includes a UV photoinitiator.